A337526 Number of length n permutations that are sorted to the identity by a consecutive-213-avoiding stack followed by a classical-21-avoiding stack.
1, 2, 5, 15, 50, 180, 686, 2731
Offset: 1
Examples
For n = 3, the permutations 123, 213, 231, 312, and 321 are correctly sorted to the identity while the permutation 132 is not.
Links
- C. Defant and K. Zheng, Stack-Sorting with Consecutive-Pattern-Avoiding Stacks, arXiv:2008.12297 [math.CO], 2020.